Vol 2 - Issue 8 July/August 1998
On the Wire - Tech Tips

Catamaran Sailing
Catamaran Pictures

Converting Stock Seaway Blocks to Low Profile Blocks

By Roy Tally
1. Disassemble the old 5:1 system so that you have 2 single blocks from the boom, one double block, and the single ratchet block and cam cleat that attaches to the traveler car.
2. Put the double block aside.
3. Carefully drill out the rivets of the single blocks using a 3/8" bit. Wrap tape around the block if you want to avoid spilling the bearings. If you are a perfectionist, go ahead and completely disassemble the blocks and clean bearings, races and side plates. Work in a shoe box to avoid losing a bearing.
4. Remove the cam cleat assembly from the ratchet block. Substitute two set screws from the base of the single or double blocks for the screws and washers that hold the cam cleat assembly to the block. The object is to provide a stop screw that will be flush with the face of the block.
5. At the hardware store, purchase three quarter twenty by three and a half inch stainless steel bolts, three matching nylon lock nuts and four flat washers (all stainless). Three and one quarter inch bolts are a perfect fit if you can find them.
6. Remove the anchor posts from the single blocks. Retain the post in the ratchet block.
7. Reassemble the blocks starting with an endplate and a single block. Use two washers on the lower bolts between the single bock and the ratchet block. Set the angle of the cam cleat assembly before adding the block to the stack. Add two more washers to the lower bolts and place the remaining single block on the stack.
8. Add the end plate and locking nuts to the stack. Don't over tighten the nuts. You should cut any extra length off of the bolts with a hack saw and file the end to a smooth finish without any burrs. You may wish to file off the edges of the flat washers below the blocks to further reduce possibility of harm.
9. Rethread the mainsheet using the double block as the upper and the new triple as the lower. Tie off the sheet at the rear bail of the boom. Use a swivel connector to hold the double to the boom. It must pivot. Now you have a very short stack and a quick 5:1 system for peanuts.

Roy Tally

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